Recessed Single-Gang Old-Work Box

Recessed Single-Gang Old-Work Box for Wall-Mounted Home-Automation Tablets

This is a recessed single-gang old-work box, designed specifically for in-wall home-automation tablets and similar devices that are powered from a standard USB charger, not a custom power PCB. The goal is to keep things as code-friendly as possible by using off-the-shelf, safety-tested hardware (Apple or other listed USB chargers, listed panel-mount power inlets, etc.) instead of mystery boards.

The box body is printed in two main halves (left/right) with snap features and separate clamping “ears,” plus a removable front plate and plate screw capture washer. It’s meant to be installed like a typical old-work box and labeled with its internal volume and maximum conductor fill so you can verify box fill against your local electrical code.

⚠️ Important: I’ve designed this to follow box-fill rules and clearances as closely as I reasonably can, but it is not UL/ETL listed and hasn’t been tested or certified. You must check your own local electrical code and regulations, and when in doubt, consult a qualified electrician. Use at your own risk.

Intended Use

• Recessed mounting location for a wall-mounted tablet or similar low-power device.
• Provides room for a standard USB charger brick to plug into a panel-mount US outlet inside the recessed box, so the charger can be:
  • easily replaced,
  • selected from a known good, listed brand,
  • and run continuously without abusing the tablet or charger.

If you later decide you want a standard switch or receptacle, the inner device plate can be removed, and the cavity and spacing are intended to be compatible with typical single-gang devices (check depth and clearance for your specific device).

Recommended Panel-Mount Power Inlet

This design was sized around this style of panel-mount US outlet:

• Amazon example (what I used):
  https://www.amazon.com/dp/B08BJF4LBC
  3-pin US panel-mount outlet, 15A 125V, approx. 1" × 1" front face with a panel cutout around 15/16" × 7/8" × ~1.3" depth, commonly sold as a “US Power Inlet / Panel Mount Outlet, 15A 125V, 3-pin.” Amazon

Equivalent parts can be found by searching for something like:

• “15A 125V US panel mount outlet 1 inch square”
• “US power socket 3-pin panel mount 25×25mm” Walmart.com+1

Electrically these are NEMA-style 5-15R geometry devices (standard North-American 3-prong 125V receptacle pattern), packaged in a small panel-mount housing. Wikipedia

Recommended Flat USB Cable

Inside the box, space is tight, so I designed around a very thin flat USB extension cable:

• AliExpress example (what I used):
  https://www.aliexpress.us/item/3256801766037946.html

Look for ultra-thin / flat USB A male-to-female extension cables, ideally with low-profile or 90° connectors. Many listings use internal codes like “AMUP” or “CMUP” to describe the connector orientation (A-Male Up, C-Male Up, etc.) – choose whichever orientation best routes from your panel-mount inlet to the charger or tablet without sharp bends.

Any similar USB A male-to-female flat cable that physically fits and is rated for your charging current should work.

Print Recommendations

Material

• Print in high-temperature materials only:
  • ✅ ASA (recommended – what the 3MF is set up for)
  • ✅ ABS
• ❌ Do not use PLA, PETG, or low-temp materials for in-wall electrical hardware.

Included .3mf profile

The provided 3MF is sliced for Bambu X1C with PolyLite ASA:

• 0.2 mm layer height
• 0.4 mm nozzle
• Inherits “PolyLite ASA @ BBL X1C” profile
• Nozzle temp ≈ 257 °C, bed ≈ 102 °C (textured plate)
• 15% grid infill, 2 wall loops

You can increase perimeters/walls and infill if you want a stiffer box or your local code/inspector prefers more robust construction.

Other notes

• Print parts in the orientation stored in the 3MF if possible.
• Use enough top/bottom layers to make solid faces where clamps and screws bear on the part.

Assembly & Hardware

• The main box is made from left and right halves that snap together.
• Two clamping “ears” are driven by 6-32 screws (standard device-box / cover-plate screws) to clamp the box to the drywall like a normal old-work box.
• A separate plate and plate screw capture washer are included for the front device plate.
• The shell is designed so that:
  • The panel-mount US outlet drops into the rectangular opening and is fixed with screws.
  • The flat USB extension cable routes from that panel-mount outlet to your charger/tablet with minimal bend and minimal bulk.
• The halves are designed to snap together without additional fasteners.
  • Optional: A bead of CA or solvent-type adhesive along the seams after test-fitting is recommended for long-term in-wall use.

Code & Safety Notes (Read This)

• This is a 3D-printed plastic box, not a listed electrical box.
• The internal volume and printed box-fill label are intended to match typical US NEC conductor-fill rules for 14 AWG and 12 AWG conductors, but:
  • local code editions vary,
  • interpretations vary,
  • and plastic types / flammability ratings for 3D-printed parts are different from UL-listed boxes.
• The design aims to be as code-respectful as I can reasonably make it, but it is:
  • not UL/ETL listed,
  • not tested or certified, and
  • should be treated as a DIY / experimental part.

Before using this in a permanent installation:

1. Confirm box fill, wiring method, and device usage with your local electrical code.
2. Use only listed, quality USB chargers and listed panel-mount mains hardware.
3. If you’re unsure, have a licensed electrician review your installation.

What’s Included

• STEP files for:
  • Left half
  • Right half
  • Clamp (×2)
  • Front plate
  • Plate screw-capture washer
• Bambu Studio .3mf project with tuned ASA settings for the Bambu X1C.

Suggested Search Terms for Compatible Parts

If you’re sourcing parts elsewhere, these phrases tend to find compatible hardware:

• “US 3-pin panel mount outlet 125V 15A 1 inch square” Amazon+1
• “ultra thin flat USB A male to A female extension”